(i) Field of the Invention
This invention relates to procedures for reducing the viscosity and density of heavy oils to make them more suitable for transportation by pipeline from the field to refineries for further processing.
This invention also relates to processes for the generation of both hydrogen and carbon dioxide by one of two alternative schemes: either only reducing the viscosity and density of the heavy oils to a small extent by minimizing thermal cracking; or totally changing the properties of the heavy oil by operating at typical hydrocracking conditions.
(ii) Description of the Prior Art
The decreasing supply of light conventional crude is spurring the use of more heavy oils and bitumen. Much of this heavy oil production is transported by pipeline from the field to refineries for further processing. For example, significant quantities of heavy oil are transported from western Canada to the United States where they are used in asphalt production. However, many of the heavy oils produced do not meet the specifications set by the pipeline companies for viscosity, density and bottoms, sediment and water (BS&W). Currently these oils are blended with large amounts of diluent (natural gas condensate or lighter petroleum fractions) to meet the specifications. However, demand and supply predictions for heavy oil and diluents indicate that a shortage in diluent will develop during the 1990's.
An increasing fraction of the heavy oils are being produced by enhanced oil recovery (EOR) techniques, e.g. steamflood, carbon dioxide flooding or fireflood. Natural surfactants present in the oil often result in stable oil/water emulsions being formed. In such oil/water emulsion, the water is present as small water droplets in a matrix of oil. Sometimes reverse emulsions are formed wherein the oil is present as small droplets in water as the continuous phase. To meet the pipeline specifications for bottoms, sediment and water (BS&W) generally requires removing the water, which was difficult and involves costly chemical and mechanical treatments. Generally (most) water is removed by a combination of gravity separation (sometimes mechanically aided) and by the addition of demulsifiers to break the emulsion. To remove the last traces of water, more severe measures are often required. In addition, certain emulsions, e.g. fireflood emulsions, are very difficult to break. Removal of the last amounts of water often is accomplished by flash evaporation, i.e., the oil is heated to above the boiling point of water. Finally after a clean, water-free oil has been obtained, the viscosity and density specifications still have to be met to allow transportation by pipeline. Again this is accomplished by mixing the oil with diluent.
The prior art has addressed the problem of how to transport such viscous material, while reducing the diluent requirements, by two general classes of treatment. The first class includes processes that do not affect the oil in any way and use water as a substitute for diluent. The second class includes processes that break up the constituent oil molecules and change its properties, thereby reducing both its viscosity and density. In both classes of treatments, the original emulsion water has to be separated first.
Processes in the first class reduce the viscosity by mixing the oil with water and surfactants to prepare an oil-in-water emulsion. This emulsion must be stable enough to withstand the diverse conditions it encounters in the pipeline system, e.g., the high shear stresses in the pumps, yet be easy to break at its destination.
Transportation of the oil using core annular flow is another proposed concept. Here an artificially created film of water surrounds the oil core concentrically. This reduces the viscosity and pressure drop almost to that which would be expected for water. These processes require that, where field emulsions are produced, these emulsions be broken first. Water, and in the case of emulsion transport, surfactants, are then added and mixed under controlled conditions to obtain a stable emulsion or core flow. In all cases where diluents or water are used, a significant part of the capacity of the pipeline is being taken up by a non-heavy oil component, significantly adding to the cost of the system. In the case of water, it might also create a disposal problem at the receiving end of the pipeline, and in the case of diluent, return lines will often be required to transport the diluent back to the field to be mixed again with heavy oil.
Processes in the second class alter the oil properties significantly and are generally of the carbon rejection or hydrogen addition type. Both procedures employ high temperatures (usually&gt;about 430.degree. C.) to crack the oil. In the carbon rejection processes, the oil is converted to lighter oils and coke, while in the hydrogen addition processes the formation of coke is prevented by the addition of high pressure hydrogen. In some coke rejection processes, the coke is burned or gasified to provide heat, or fuel that can be used elsewhere in the process. Both of these upgrading processes significantly increase the distillate yields, because of the thermal cracking of the heavy oil molecules that takes place, which results in significantly altered molecular weight structures and properties. However, because of the extensive cracking that takes place, these high conversion processes destroy the asphalt properties that many of the original heavy oils exhibit. This is a serious concern since asphalt is a high priced commodity.
All hydrogen addition processes require hydrogen to allow the process to proceed without coke formation. Some hydrogen addition processes are described in the prior art that use coke or effluent streams to generate carbon monoxide, which in turn is used to make hydrogen.
For example, U.S. Pat. No. 2,614,066, patented Oct. 14, 1952 by P. W. Cornell, provided a continuous method of hydrodesulfurization, in which the hydrogen utilized in the process was largely obtained from contaminant produced concomitant with the hydrodesulfurization process. The patented process comprised removing sulfur from petroleum hydrocarbons containing sulfurous material at an elevated temperature with a hydrogen-containing gas in the presence of a contact material having hydrogenating characteristics, cooling the effluent to obtain a first gas portion and a hydrocarbon liquid portion containing dissolved gases, separating the hydrocarbon liquid portion, and removing the dissolved gases from the hydrocarbon liquid to form a second gas portion. Substantial amounts of the hydrocarbon portion of this second separated gas portion were then converted into hydrogen through a reforming and shift reaction. The formed hydrogen was recycled for the hydrodesulfurization of the feed petroleum hydrocarbons.
U.S. Pat. No. 3,413,214, patented Nov. 26, 1968 by R. B. Galbreath, provided for the hydrogenation of liquid hydrocarbons which was carried out in the presence of hydrogen and a controlled amount of oxygen to hydrogenate a major portion of the liquid hydrocarbon feed and to oxidize a minor portion thereof, thereby producing a gaseous product containing carbon monoxide. The carbon monoxide content of the gaseous product was subsequently reacted with steam in a separate reactor to form additional hydrogen which was recycled to the hydrogenation zone.
U.S. Pat. No. 3,694,344, patented Sep. 26, 1972 by W. H. Munro, provided a process for the hydroprocessing of hydrocarbon. In the description of the invention, a steam reformer, water-gas shift converter and an acid-gas removal system is combined utilizing compression between the water-gas shift converter and the acid-gas removal system to produce relatively high purity hydrogen for use in a hydrogen-consuming process. In essence, therefore, the invention provides a method for the hydrogenation of hydrocarbons utilizing a specified hydrogen stream which is obtained from a specific hydrogen-producing plant. The hydrogen-producing plant was a steam reforming unit which utilized centrifugal compression between conversion zones and the carbon dioxide adsorption zones of the unit. In the hydrocracking process, the hydrocarbons to be converted into lower-boiling material are contacted with a suitable catalyst under hydrocracking conditions chosen to produce an effluent stream containing unreacted hydrogen, normally gaseous hydrocarbons and normally liquid hydrocarbons.
Suitable catalytic composites comprised at least one metallic component selected from the metals of Groups VI-B and VIII of the Periodice Table combined with a suitable refractory inorganic oxide, e.g. alumina, silica, and mixtures thereof. However, this patent does not teach operation under conditions enabling the recovery, for use later of a gaseous stream of carbon dioxide.
U.S. Pat. No. 3,694,374, patented Sep. 26, 1972 by Y. Yamazaki et al (and its corresponding Canadian Patent No. 943,943 patented Mar. 19, 1974) provided a catalyst for the catalytic cracking or steam reforming of hydrocarbons. According to the patented invention, with the patented catalyst, a desirable oxidation reaction, i.e. water gas reaction is especially promoted. Therefore, the amount of carbon deposited on the catalyst is very small. Formation of tar is also negligible. Thus, a gas having a high content of hydrogen (H.sub.2) and consisting of methane (CH.sub.4), ethylene (C.sub.2 H.sub.4), carbon dioxide (CO.sub.2) and a small amount of carbon monoxide (CO) is obtained. The patented catalyst was an alkali polyaluminate or a catalyst prepared by adding at least 2% of an alkali polyaluminate, calculated as an alkali metallic oxide (Na.sub.2 O or K.sub.2 O), to other refractory carriers. However, this patent does not teach operation under conditions enabling the recovery, for use later of a gaseous stream of carbon dioxide.
U.S. Pat. No. 4,207,167 patented Jun. 10, 1980 by R. W. Bradshaw, provided a combination process for hydrocarbon cracking, hydrogen production and hydrocracking. The invention provided a combination of process steps which comprises catalytically cracking a hydrocarbon oil, regenerating a used catalyst having coke laydown thereon, the regeneration being effected under conditions to produce a gaseous effluent containing carbon monoxide, subjecting the effluent to a water shift reaction producing carbon dioxide and hydrogen, fractionating cracked oil vapours earlier obtained to obtain among other fractions, a cycle oil and hydrocracking the cycle oil in the presence of the hydrogen earlier produced. That invention provided in combination, steps as follows: catalytic cracking a hydrocarbon oil, regenerating catalyst used in the cracking under conditions to produce gases rich in carbon monoxide, effecting the water shift upon the gases to produce carbon dioxide and hydrogen, fractionating vapours obtained in the cracking of hydrocarbon oil to obtain, e.g. gases, cracked gasoline, a light-cycle oil, a heavy-cycle oil and a heavier fraction of hydrocarbons and hydrocracking at least one of the light and heavy cycle oils with hydrogen obtained in the water shift reaction. The catalyst used may be nickel-molybdenum or cobalt-molybdenum. However, this patent does not teach operation under conditions enabling the recovery, for use later of a gaseous stream of carbon dioxide.
U.S. Pat. No. 4,309,198 patented Jan. 5, 1982 by G. Moss, provided a method of converting liquid and/or solid fuel to an inerts-free gas. In the described inventive process, liquid and/or solid fuel is converted to inerts-free reducing and/or synthesis gas (which may contain at least one of the following compounds: CO, H.sub.2, CH.sub.4) by treating the fuel in a conversion zone under fuel conversion conditions in the presence of a reducible (and preferably reoxidizable) solid oxygen comprising compounds in the presence of a gaseous phase substance which, under the conversion conditions, promotes the transfer of oxygen from tee solid oxygen-comprising compound to the fuel and/or to a partially-converted component of the fuel. The patent discloses the production of reactant gas by the water gas reaction, using a catalyst known to catalyze the water gas reaction. However, this patent does not teach operation under conditions enabling the recovery, for use later of a gaseous stream of carbon dioxide.
U.S. Pat. No. 4,569,753 patented Feb. 11, 1986 by L. E. Busch et al, provided a process for oil upgrading by thermal and catalytic cracking. The patented process is said to be a unique sequence of operations designed to dispose of and/or handle the undesirable components of reduced crude in a manner permitting conversion of high boiling hydrocarbon components in association therewith to more desirable gaseous and liquid fuel products.
More particularly, the process comprises a thermal visbreaking operation with fluidizable inert solids followed by a fluidized zeolite catalytic cracking operation processing demetallized products for the visbreaking operation, regenerating solid particular of each operation under conditions to provide CO rich flue gases relied upon to generate steam used in each of the fluidized solids conversion operation and downstream product separation arrangements, separating the wet gas product stream of each operation in a common product recovery arrangement and processing the high boiling feed product of visbreaking comprising up to 100 ppm Ni+V metal contaminant over a recycled crystalline zeolite cracking catalyst distributed in a sorbent matrix material comprising a high level of Ni+V metal contaminant. However, this patent does not teach operation under conditions enabling the recovery, for use later of a gaseous stream of carbon dioxide.
Canadian Patent No. 916,083 patented Dec. 5, 1972 by D. A. Messing et al, provided a hydrocracking process in the presence of hydrocarbon containing a minor amount of carbon monoxide. That patent taught the production of hydrogen by the gasification of hydrocarbons to a synthesis gas composed for the most part of carbon monoxide and hydrogen, either by the partial oxidation of hydrocarbons or by the reforming of hydrocarbons with steam. Conventionally, the synthesis gas was passed in the presence of steam into contact with a shift conversion catalyst, e.g. iron oxide, which resulted in the production of a gas composed for the most part of hydrogen and carbon dioxide. The carbon dioxide content was reduced to a negligible level to yield a gas containing about 96-98% hydrogen and about 2% CO, with smaller amounts of other impurities. The patented process involved treating the hydrocarbon oil in the presence of hydrogen using a hydrocracking catalyst comprising an iron group metal under hydrocracking conditions, the hydrogen containing at least 50 ppm CO.
As taught in that patent the catalysts contained two components, a hydrogenating component and a cracking component. The hydrogenating component was an iron group metal, for example, I0 nickel or cobalt. The hydrogenating component was present in an amount between about 5 and 40% by weight of the catalyst composite.
The cracking component was at least one amorphous inorganic oxide having cracking activity, for example, silica, alumina, magnesia, zirconia, and the like, which if necessary had been treated with an acidic agent, e.g. hydrofluoric acid, to impart cracking activity thereto. A preferred mixture of amorphous inorganic oxides taught in that patent contained 60-90% silica and 10-40% alumina. However, this patent did not teach operation under conditions enabling the recovery, for use later, of a gaseous stream of carbon dioxide.
Canadian Patent No. 1,195,639, issued Oct. 22, 1985 by H. S. Johnson, et al, provided a process for upgrading heavy viscous hydrocarbonaceous oil. The patented process involved contacting the oil with a carbon monoxide-containing gas and steam in a reaction zone at hydrocracking conditions, e.g. at a temperature of at least about 400.degree. C. and a pressure between substantially 5MPa and 20 MPa, in the presence of a promoted iron catalyst, to yield a hydrocracked product. The required hydrogen to prevent coke formation was made from carbon monoxide and added water inside the upgrading reactor. No hydrogen or carbon dioxide was recovered.
Canadian Patent No. 1,124,195, issued to Khulbe et al, described a hydrocracking process that operated from about 400 to about 500.degree. C., where synthesis gas was used to supply the hydrogen for the cracking reactions. The synthesis gas was made in a separate reactor.
None of the patented processes described above are suitable for reducing both the viscosity and density of heavy oils without substantially breaking up the constituent molecules of the oil. In all the hydrocracking processes described above, the oil properties were changed significantly. None of the patents taught the use of a bifunctional hydrogenation/water gas shift reaction catalyst. Furthermore, in none of the described processes, were hydrogen and carbon dioxide recovered separately for use in alternative processes.